Vacumn Leak ?

Chasing down a couple of vacumn leaks on a 1988 Cherokee, 4.0

Under the radiator overfill bottle is a small blue vacmun line that is not connected to anything. Anyone have any ideas what it is for?

I searched but couldn't find a diagram that might show me.

There are several small lines under there, but this seems to be the only one that is not connected to anything.

Try to post a picture a little later.

Thanks for any help in advance.

It's a vent. It should have a check valve on it, and it's not supposed to be connected.